Synthesis of disaccharides using β-glucosidases from Aspergillus niger, A. awamori and Prunus dulcis.

Abstract

Glucose conversion into disaccharides was performed with β-glucosidases from Prunus dulcis (β-Pd), Aspergillus niger (β-An) and A. awamori (β-Aa), in reactions containing initial glucose of 700 and 900gl-1. The reactions' time courses were followed regarding glucose and product concentrations. In all cases, there was a predominant formation of gentiobiose over cellobiose and also of oligosaccharides with a higher molecular mass. For reactions containing 700g glucose l-1, the final substrate conversions were 33, 38, and 23.5% for β-An,β-Aa, andβ-Pd, respectively. The use of β-An yielded 103g gentiobiose l-1 (15.5% yield), which is the highest reported for a fungal β-glucosidase. The increase in glucose concentration to 900gl-1 resulted in a significant increase in disaccharide synthesis by β-Pd, reaching 128g gentiobiose l-1 (15% yield), while for β-An andβ-Aa, there was a shift toward the synthesis of higher oligosaccharides. β-Pd and the fungal β-An andβ-Aa β-glucosidases present quite dissimilar kinetics and selective properties regarding the synthesis of disaccharides; while β-Pd showed the highest productivity for gentiobiose synthesis, β-An presented the highest specificity.